1. Field of the Invention
An electromechanical grasping device that simulates the movements of a human hand and is suitable for use as an artificial hand prosthesis that includes four jointed movable members simulating the fingers of a hand and a fifth jointed member simulating the thumb, each of said jointed members being individually movable to provide movement comparable to a human hand. The device employs high torque, low current motors which can be controlled by mild pulses from human extremities for controlling movement. A gear rack for each jointed member driven by an individual high torque motor is connected by a stiff wire cable providing individual finger motion allowing rapid movement while retaining firm grasping when employed together.
2. Description of the Prior Art
Many attempts have been made to provide a suitable prosthetic device to be used as a mechanical artificial hand. Because of the unique movements possible of the hand digits including the opposable thumb, the hand has proven to be a very difficult limb to simulate or emulate with the use of an artificial prosthesis. Other considerations when designing an artificial hand are that the device must be comparable in weight to a real hand, have fast movement as in the fingers and the thumb, while still having a firm gripping force to allow practical use of such a prosthesis. U.S. Pat. No. 2,549,716, issued to Simpson, Apr. 17, 1951, shows a mechanical artificial hand that uses springs tensioned against a cable drive mechanism interconnected to mechanically pivoted digits. U.S. Pat. No. 2,859,450, issued to Becker, Nov. 11, 1958, shows an artificial hand mechanism and fingers which also use springs with mechanical leverage connections and rods for actuation. U.S. Pat. No. 3,418,662, issued to Bottomley et al., Dec. 21, 1968, shows a prosthetic hand with the control system activated by electromyogram signals. The mechanical aspect shows a circular gearing mechanism that is connected to a control rod that moves two fingers against a thumb. Finally, U.S. Pat. No. 3,822,418, issued to Yakobson et al., July 9, 1974, shows an artificial hand having a complex electromechanical drive control including a helical gear system with spring actuations.
None of the references shown in the prior art truly duplicate the unique movement of the human hand. Further, they are characterized by complexity in construction and operation and may include weight limitations.
The present invention overcomes these problems by providing a lightweight hand prosthesis that uses individual high torque motors with gear racks connected to stiff cables that can actuate a plurality of hinged digit members quickly with residual rigidity and force generation and which includes movement of the thumb digit member in an opposable direction to the finger digit members.